8.1 Gi-G needing some guidance please

[xSkallywagsX]

I have 2 engines that appear to have the same issue and need help from the collective mind. both engines are fuel injected and 5.7 mec and 8.1 Volvo G-IG. symptoms are no power unable to get above 2500rpms
pulled all plugs all plugs are black and fouled replaced and became fouled again after 30 min to an hour of running, they are the correct plugs for each motor , we have checked the bottoms and running gear for obstructions and over growth. both have been hooked up to the computer and show no codes and faults, also compression test have been done and have a 15psi swing and are in range. also have tired fresh fuel and bypass the tank. also the the merc.5.7 only has about 10 hrs of run time on it. all and any suggestions are welcome

 

[alldodge]

Welcome
I have never said this before but, you need to split this topic into 2 threads.

This one is good for the VP 8.1 GI-G, but need to start another for the Merc 5.7

Tell us more about the boat and drive. How long have you had the boat and these issues?
What is the fuel pressure at idle and running?